1. Field of the Invention
This invention relates to improvements in marine, which includes submarine, apparatus, such as pipelines and associated equipment
2. The Prior Art
For the recovery of hydrocarbon from beneath the seabed, it has been necessary to install prefabricated pipelines within and between offshore oil and gas fields and onshore processing facilities.
To meet the need to install pipelines with a high degree of reliability, it is possible to use barges and vessels with several aligned welding, inspection and coating stations that can fabricate a pipeline from a large number of short lengths, typically 11 meters long. The welded joints of the pipeline have then to be inspected and coated before the pipeline is lowered to the seabed down and over a curved stinger or ramp. As an alternative, suitable for pipelines of smaller diameter, the pipelines will be fabricated into long lengths, which are then reeled onto a large drum or spool on board a vessel. The pipeline is unreeled from the vessel, straightened to remove the curvature created by the reeling process, and then lowered onto the seabed.
A further alternative is to fabricate, at a suitable shore site, a bundled assembly formed of a pipeline or group of pipelines housed within a large diameter outer steel pipeline, known as a carrier pipe. The void space within the carrier pipe and around the inner pipelines is sealed to prevent seawater ingress and to provide buoyancy. The bundled assembly is then towed from the shore site to the offshore site, where the carrier is then flooded.
In use, pipelines and associated equipment often need to be insulated to maintain temperatures of the fluid flowing within them. Thermal insulation of the equipment is currently provided by the application to the outside surface of the pipeline or equipment of one or a plurality of layers of suitable insulation material. These insulation materials are typically elastomers, which are applied to the pipeline by various processes including extrusion, impingement or wrapping.
A further alternative, where high levels of thermal insulation is required, is to house a pipeline within an outer sleeve pipe, the annulus between which is filled either totally or partially with insulation material. This method of providing thermal insulation, is known as a ‘Pipe-in-Pipe’ arrangement. The ‘Pipe-in-Pipe’ arrangement is particularly appropriate for installation in deep water and/or operation at high temperatures and pressures.
It is an objective of the present invention to provide a marine and submarine apparatus, including pipelines and associated equipment with an alternative form of high performance thermal insulation, which does not need to be housed within an outer sleeve Pipe-in-Pipe arrangement.